2013-01-14 by Todd F. Carney
Jeff,
Well, I think some brave soul should experiment with it. Oxidation is only
a problem prior to exposure. If the cover film were removed a few seconds
before being sandwiched and clamped under glass, there may be no adverse
effect at all. It may be that DuPont says to leave the film on because they
can't control the timing of how the resist is used and when the cover film
is removed.
The pcb material sold by FarCircuits (http://www.farcircuits.net/) is
laminated with Dupont PM115 resist. It's also available from other
retailers, but I think I'll get some from Far because I need a other things
from them. I have a few boards I need to do myself. I think I'll try one
with the cover film removed before exposure. If it seems okay, I'll try a
few more. I'll let you know.
73,
Todd
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K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
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QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
On Sun, Jan 13, 2013 at 6:44 PM, Jeff Heiss <jeff.heiss@comcast.net> wrote:
> **
>
>
> The SEM images are great. I'm left wondering what the time frame is
> regarding the oxygen exposure to resist. Minutes, hours? I suppose the
> oxygen contamination issue is large enough where it is better to leave the
> cover sheet on and accept the more diffused and less collimated light?
>
> Jeff
>
>
> -----Original Message-----
> From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
> On Behalf Of Todd F. Carney
> Sent: Sunday, January 13, 2013 8:38 PM
> To: Homebrew_PCBs@yahoogroups.com
> Subject: Re: [Homebrew_PCBs] photoresist application
>
> On Sun, Jan 13, 2013 at 5:19 PM, Todd F. Carney k7tfc@...> wrote:
>
> > The cover sheet protects the resist from oxygen and from oxidizing the
> > "free radicals" on which the photo-polymers depend. Here is an excellent
> > document from DuPont on this:
>
> Sorry, Folks. Wrong URL for the DuPont document. Here's the right one:
>
>
> http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/techtalk/TT1
> 207.pdf
>
> 73,
>
> Todd
> ----------------------------------------------------------
> --------
> K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
> ----------------------------------------------------------
> --------
> QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
>
> >
> >
>
> http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/techtalk/TT1
> 007.pdf
> >
> > You will note that from an optical standpoint, leaving the cover sheet on
> > is not optimum as it inevitably degrades the sharpness of the image. This
> > is one reason why commercial or professional exposure units use arc light
> > or a similar "point source" instead of diffused light like we home
> brewers
> > use almost exclusively. Actually, for the stuff we typically do, the
> > difference would probably never be noticed.
> >
> > 73,
> >
> > Todd
> >
> >
> ----------------------------------------------------------
> --------
> > K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
> >
> >
> ----------------------------------------------------------
> --------
> > QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
> >
> >
> > On Sun, Jan 13, 2013 at 3:58 PM, Jeff jeff.heiss@...> wrote:
> >
> >> **
>
> >>
> >>
> >> Photoresist is shipped with a clear protective covering film on the top
> >> and bottom. The covering film is removed by the user before the
> photoresist
> >> is applied. A comment by a poster in a forum says the top covering
> should
> >> be kept on during exposure and removed before developing. Is that true?
> Why
> >> is that?
> >>
> >> "Note that the dry film resist should be exposed with the cover sheets
> >> on, and then held in a dark place for 15 minutes before removing the
> cover
> >> sheets and developing."
> >>
> >>
>
> http://www.electro-tech-online.com/general-electronics-chat/14427-photoresis
> t-pcb-etching-process.html
> >>
> >> Jeff
> >>
> >>
> >>
> >
> >
>
> [Non-text portions of this message have been removed]
>
> ------------------------------------
>
>
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>
>
>
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